Line noises in a very high speed digital subscriber line 2 (VDSL2) mainly include crosstalk, an impulse noise, a radio-frequency noise and the like. Simply speaking, crosstalk is an effect from a signal in a twisted pair on a signal in another twisted pair as a result of electromagnetic interference among wire pairs because twisted pairs used in the VDSL2 are unshielded from each other. It is generally considered that crosstalk exists among wire pairs in a same cable bundle, and one twisted pair is subject to interference from multiple wire pairs. Because a relatively high frequency band (which may be up to 30 MHz) is used in a VDSL2 technology, external interference caused during sending through multiple wire pairs mainly comes from interference between neighboring wire pairs, which greatly reduces a sending rate of multiple wire pairs in a VDSL2 system.
In a vector technology, through a vectored VDSL2 system, joint processing (for example, coordinated sending) is performed on a signal in a downlink direction, or joint processing (for example, coordinated receiving) is performed on a signal in an uplink direction, so as to eliminate far-end self-crosstalk (that is, far-end crosstalk generated among lines in a vectored group), thereby enhancing performance.
FIG. 1 is a schematic structural diagram of an existing board-level vectoring processing system. An access device accesses a network system, and a line card (that is, a board) of the access device completes, through a built-in vectoring control entity (VCE), coordinated processing of uplink/downlink sending and receiving on port lines of the board, computes crosstalk effects among the port lines, and performs cancellation on far-end crosstalk among the port lines, so as to eliminate effects of crosstalk on signal sending and receiving on the port lines. However, this solution is only applicable to a scenario in which subscribers on a same cable bundle are all connected to a same line card, so the access device is accessible to a few subscribers, which poses a great limitation.
FIG. 2 is a schematic structural diagram of an existing system-level vectoring processing system. An access device is configured with an independent vectoring processor (VP) as a centralized vectoring processing board, and line cards D1-Dn of the access device are respectively connected to the centralized vectoring processing board through different ports. The centralized vectoring processing board completes coordinated processing of uplink/downlink sending and receiving on all port lines of the access device, computes crosstalk effects among the port lines, and performs cancellation on far-end crosstalk among the port lines, so as to eliminate effects of crosstalk on signal sending and receiving on the port lines. Compared with the solution shown in FIG. 1, in this solution, the number of subscribers that can access the access device is increased. However, this solution requires that subscribers on a same cable bundle access a same access device, so when subscribers on a same cable bundle are connected to different access devices, this solution cannot satisfy a requirement of the scenario.